CN102301216A - leak detector - Google Patents

Abstract

Provided is a leak detector for detecting and locating leaks in a water supply pipe of plastics, and the leak detector comprises a first sensor at a first position arranged to detect a leak signal travelling along a pipe, a second sensor arranged to detect a leak signal travelling along the pipe at a second position spaced from the first position, and a processing device adapted to receive the signals from the first sensor and the second sensor. The processing device may be adapted to determine the velocity of the signals from characteristics of the leak signals. The processing device is adapted to use the velocity and distance between the first sensor and the second sensor to determine the location of a leak. The characteristics may be the relationship between the phase and frequency of the leak signals.

Description

The small opening detecting device

Technical field

The present invention relates to the small opening detecting device, be used for detecting and locating the position of feed pipe small opening, in particular for detecting and the location plastics, such as the position of small opening in tygon and particularly intermediate density tygon (MDPE) feed pipe.Especially, the present invention relates to use simple crosscorrelation small opening positioning detector.The invention still further relates to a kind of method, be used to detect and locate plastics, especially small opening position in the poly feed pipe of tygon such as intermediate density.

Background technology

The utilization of water in many areas, the world is attempted satisfying in the demand of potable water in the face of growing challenge at them.This is caused by many factors, and such as arid cycle, the population growth of climate change, prolongation, migrate and temperature rises, these factors apply the pressure that increases day by day to existing water source.Another key factor is the leakage from water transmission and distribution network.Leakage is owing to the aging of network and destroys and occurs, and constitutes the major part that damage by water consumes in the water supply network.Therefore, reducing the leakage from water resource system, is to improve extremely important strategy in the sustainable use of water.

Small opening produces the sound of propagating along the soil (along the upstream and downstream both direction) of water column (water column) in pipe and shell and encirclement pipe in the feed pipe.This sound is commonly referred to as the small opening signal, it comprise acoustics with the vibration signal.The enough acoustics small opening checkout equipments of its energy, bar (listening stick) and correlator are detected such as monitoring; Generally use by water and wastewater industry.These small opening signals can be detected reach as high as distance, depend on the feature of pipe.In recent years,, compare with cement,, had a preference for day by day owing to their lower in use rate of ageings with old tube material such as metal (cast iron etc.) such as the plastic tube of MDPE.By the sound that blow-by tube causes, very fast decay in plastics especially MDPE pipe.So, use at present available acoustics emission detection system, detection and location are very difficult such as the small opening in the poly plastic tube.

The accurate location of small opening is even more important, because the excacation of needed arrival buried pipe, so with regard to time, expense with relate to regard to the physics of finding out small opening makes great efforts, be expensive.

Summary of the invention

According to a first aspect of the present invention, we provide a kind of small opening detecting device, are used for detecting and locating the small opening of plastic water supply pipe, and this small opening detecting device comprises: first sensor is arranged at and detects the small opening signal of propagating along pipe on the primary importance; Second sensor, be arranged at the isolated second place of primary importance on detect along the small opening signal of this pipe propagation; With the treating apparatus that is fit to from the first sensor and the second sensor received signal.This treating apparatus can be fit to determine the speed of small opening signal from the feature of small opening signal.This treating apparatus is fit to use distance between this speed and the first sensor and second sensor, determines the location of small opening.

This is favourable, because this small opening detecting device use from the speed of the small opening signal of the feature derivation of this signal, can accurately detect and determine the location of small opening in pipe.By the small opening signal of sensor, comprise acoustics and signal vibration that causes by small opening and noise signal.Although have been found that the noise signal of high level, this treating apparatus is accurate, and can determine the speed of small opening signal.So,, be used to calculate the speed of small opening signal by the measurement that the feature and the distance between the sensor of small opening signal are made.

Known correlator uses the preset speed values that is stored in the database.The empirical value that these are predetermined is to use method various different theories and/or experiment calculated.The appropriate value of known correlator medium velocity selected depends on the size and the material character of pipeline section between two sensing stations of user's input.In the practice, water distribution networks has uncontinuity and the joint on many pipe physical propertys.The speed of small opening signal is quite big with these change in physical of pipe.Because these uncontinuities, such as the imperfect record of the change (for example because repair work) of tube material between two measuring positions,, be correlated with existing method at every turn, accurately to determine velocity of propagation, be trouble very.The present invention determines the speed of small opening signal by the measured feature from this signal itself, overcomes this problem.

This treating apparatus uses the phase place of small opening signal and the feature of the linear relationship between the frequency, can be fit to determine the speed of small opening signal.It is favourable doing like this, because have been found that in plastics especially MDPE pipe, the use of linear phase-frequency relation obtains the precise results in the frequency range that the small opening signal extensively exists.

Preferably, this feature is the phase place and the frequency of small opening signal, and this treating apparatus can use phase place and this speed of the ratio calculation between the frequency of small opening signal.

This treating apparatus preferably is arranged to determine the Fourier transform of the small opening signal that detects on the first and second two sensors, and also is arranged a Fourier transform that the Fourier transform that obtains is multiplied each other and uses this quilt to multiply each other in the speed of determining the small opening signal.

Preferably, this first sensor and second sensor respectively comprise accelerometer.Have been found that this class sensor especially is fit to measure the vibration signal that produces by such as small opening in the plastic tube of MDPE.

This first sensor and second sensor preferably respectively comprise signal conditioning unit and transmitting element, and this signal conditioning unit is arranged the signal filtering to the respective sensor reception, and this transmitting element is fit to send this filtered signal to treating apparatus.It is favourable doing like this, because signal conditioning unit can make and have only the relevant range of frequency to be sent to treating apparatus signal filtering.Preferably, this signal conditioning unit comprises wherein the passband low-pass filter below 760Hz basically.The spectral range of the small opening signal of deriving from all types blow-by tube, the frequency that contains usually is lower than 760Hz basically, thereby has only relevant frequency to be considered.

The small opening detecting device preferably comprises transmitting element and receiving element, be arranged to make first sensor and second sensor together with they related signal conditioning units, can wirelessly operate the remainder of small opening detecting device, and wherein this transmitting element is fit to the phase place and the phase place that keep by the small opening signal of second sensor of maintenance by the small opening signal of first sensor detection.

Preferably, this treating apparatus is fit to the signal digitalized and storage from first sensor and the reception of second sensor.It is favourable doing like this, can be configured to depend on the amount that noise occurs because obtain the cycle of signal, and because data are stored, and it can be handled in time processing means after a while, or processed several is to guarantee accuracy.

Treating apparatus preferably comprises meticulous filter unit, is fit to the small opening signal filtering to being digitized, and this meticulous filter unit comprises Bezier finite impulse response (FIR) (FIR) wave filter.Especially, this meticulous filter unit preferably includes the 9th rank Bezier low-pass filter and the 8th rank Bezier Hi-pass filter.Having been found that this selection of wave filter, to the small opening signal that is caused by small opening in the signal of isolating first and second sensor, is favourable.This Bezier FIR wave filter has linear phase response, thereby is useful to isolating the small opening signal.

Preferably, this treating apparatus comprises the windowing unit, is fit to the Hanning window mouth is applied to the signal that obtained by first sensor, obtaining the signal of a plurality of windowings, and is applied to the signal by the acquisition of second sensor, to obtain the signal of a plurality of windowings.It is to be applicable to Fourier transform and to ask average a plurality of signals that this windowing unit is fit to the small opening signal decomposition from each sensor.

This treating apparatus preferably comprises converter unit, is fit to split window signal and uses Fast Fourier Transform (FFT).From the signal that first and second sensors start, thereafter can be processed at frequency domain, simplified processing like this.

This treating apparatus preferably comprises asks averaging unit, and this asks averaging unit to be suitable for: after each windowing signal application Fourier transform, calculating is average from the root mean square of a plurality of windowing signals of first sensor; And after each windowing signal application Fourier transform, calculating is average from the root mean square of a plurality of windowing signals of second sensor.

This treating apparatus preferably comprises the speed determining unit, is arranged to determine the speed of small opening signal from the feature of small opening signal and the distance between the first sensor and second sensor, and wherein this speed is obtained by following equation:

$c=\frac{-\mathrm{\ωD}}{{\mathrm{\φ}}_{x_1{x}_2}^m\left(\mathrm{\ω}\right)}---\left(1\right)$

Here c is made of the speed of signal, and ω represents angular frequency, and D is the distance between first and second sensor, and

Be the first signal (x from first sensor ₁) Fourier transform with from the signal (x of second sensor ₂) the phase place of product of Fourier transform.

Preferably, this treating apparatus comprises the small opening positioning unit, be fit to receive the speed of calculating by the speed determining unit, this small opening positioning unit also is fit to carrying out simple crosscorrelation from the signal of first sensor and signal from second sensor, and use this cross correlation results and this speed, calculate the location of this small opening with respect to the first sensor position or second sensing station.

The small opening signal is using correlation technique to determine to play an important role in the small opening position with the speed and the decay of pipe middle distance.The prior knowledge of the physical property of art methods requirement pipe and known small opening signal/transient affair source, these are not usually to obtain from practice easily.Therefore, according to new this method of the linear phase frequency relation of small opening signal, be especially favourable.In the speed and the decay of finite length pipe medium wave propagation, can do pressure survey and be determined along institute on two location of the length of waiting to reconnoitre pipe.The linear phase frequency relation of the product of the Fourier transform of the small opening signal that speed can be measured from two location uses least square linear regression to obtain.Decay is calculated by comparing two locational transport functions of small opening signal measurement.

According to a second aspect of the present invention, we provide a kind of method that detects small opening position in the plastic tube, comprise step:

Along monitoring the small opening signal on the primary importance of pipe;

Along pipe with the isolated second place of primary importance on monitor the small opening signal;

Determine the sensor spacing distance between the primary importance and the second place;

Determine the speed of small opening signal from signal characteristic; With

Use this sensor spacing distance and speed, the location of identification small opening.

This monitors the step of the signal of indication small opening, can carry out on predetermined measurement period.

The localization step of identification small opening preferably includes the use related function, determine the time delay between the small opening signal that receives on the first sensor and second sensing station, with use this sensor spacing distance, this speed and this time delay, the location of identification small opening.

This method preferably comprises carry out the step of simple crosscorrelation at signal that obtains on the primary importance and the signal that receives on the second place.

Preferably, this method comprises by having determined whether distinguishing peak value obtained, confirms small opening detected step in related function.This step can be realized by the user of this device or suitable peak detection algorithm.

According to a third aspect of the present invention, we provide the small opening detecting device of small opening in a kind of intermediate density tygon feed pipe, and this small opening detecting device comprises: first sensor is arranged at and detects the small opening signal of propagating along pipe on the primary importance; Second sensor, be arranged at the isolated second place of primary importance on detect the small opening signal of propagating along pipe; With suitable treating apparatus, the simple crosscorrelation on the frequency range of the small opening signal between this treating apparatus suitable use 0Hz and the 350Hz, determine the location of small opening from the first sensor and the second sensor received signal.

This is favourable, contains the position that enough information is used for accurately discerning the MDPE small opening because have been found that this frequency range.So, the small opening detecting device of small opening in the MDPE pipe of the present invention, small opening accurately also can repeatedly be located in the place that can lose efficacy at the correlator of prior art.

Preferably, this frequency range is between 20Hz and 140Hz, the most preferably between 40Hz and 110Hz.These narrower frequency ranges can realize the accurate location of small opening in the MDPE pipe, make small opening Signal Processing amount minimum simultaneously.Preferably, the first sensor and second sensor comprise accelerometer, are fit to operate in reliably on the following frequency of 110Hz.This is favourable, because when these accelerometers are suitably configured, can accurately measure the frequency in the third aspect present invention institute range of definition.

Description of drawings

Then only with way of example, describe the present invention in detail now with reference to accompanying drawing, in the accompanying drawing:

Fig. 1 shows the embodiment of small opening detecting device and the sketch of blow-by tube;

The process flow diagram that Fig. 2 shows is described the embodiment of the method for operating of small opening detecting device; With

How Fig. 3 shows from the sketch of the speed of the feature calculation small opening signal of small opening signal.

Embodiment

Be used for discerning the small opening detecting device 1 of the position of managing 3 small openings 2, as shown in Figure 1.In this embodiment, pipe 3 is plastics, especially intermediate density tygon (MDPE).This small opening detecting device 1 comprises the first sensor 4 and second sensor 5.This first and second sensor 4 and 5 all is an accelerometer.Specifically, they are based on the piezoelectric accelerometer type sensor of ceramic crystal.Sensor 4,5 detects the sound and the vibration (being the vibroacoustics signal) of propagating along pipe 3, and, if small opening 2 exists, also detect the small opening signal that comprises the sound of indicating small opening.The small opening signal packet that is detected by sensor 4,5 contains noise, and this noise comprises the combination of pipe resonance and neighbourhood noise, and neighbourhood noise is such as from traffic, people with because the client consumes the current of generation.

If the signal indication that we make from the detection of first sensor 4 is x ₁, it is the function of time t, and comprises by small opening signal (s ₁) contribution and by noise (n ₁) the contribution sum.Therefore,

x ₁(t)＝s ₁(t)+n ₁(t) (2)

Similarly, the signal from the detection of second sensor 5 can be expressed as x ₂, here

x ₂(t)＝s ₂(t)+n ₂(t) (3)

By first and second sensors 4 and 5 signals that detect, processing means 6 receives, and treating apparatus 6 is fit to calculate the speed of the small opening signal in the signal that detects.Treating apparatus 6 is fit to the calculating of the speed of this small opening signal of use, determines the location of small opening 2.

The first sensor 4 that illustrates is attached to first hose saddle 7, and this first hose saddle 7 is connected on the length of the pipe 3 that small opening 2 is arranged probably.Second sensor 5 is attached to second hose saddle 8, and this second hose saddle 8 is connected on the equal length of pipe 3.Sensor 4,5 comprises the magnetic adsorption piece that they is fastened to hose saddle 7,8.Sensor 4,5 best energy measurements also can operate on the frequency that is low to moderate 1Hz less than the acceleration of 0.01g.First sensor 4 records first signal, and second sensor, 5 record secondary signals.

First sensor 4 is connected to first signal conditioning unit 10, and second sensor 5 is connected to secondary signal regulon 11.First signal conditioning unit 10 and secondary signal regulon 11 comprise analog filter, are arranged to limit the bandwidth of the signal of the detection that is received by sensor 4,5.First wave filter the 10, the 11st in the present embodiment, low-pass filter is configured to by the frequency below the 760Hz.This is favourable, because have been found that the frequency that contains the small opening signal of all general type tube materials of having found up to the frequency range of 760Hz.Therefore, be reduced, be kept significant frequency simultaneously from the quantity of information that sensor 4,5 sends.First and second signal conditioning units 10 and 11 also are fit to amplifying signal.Gain is set to 20dB, but it can be regulated.The amplifier of signal conditioning unit 10,11 is equipped with the transformer of balance input and output, with produce low noise, low distortion at 0dB to the adjustable gain between the maximum 66dB.They are operated in 10Hz to the audio bandwidth of 50Hz and wide dynamic range above 120dB is provided.

First and second signal conditioning units 10 and 11 can comprise the adjustable gain amplifier.It is more flexible to make them detect dissimilar small openings like this.In addition, first and second signal conditioning units 10 and 11 can have adjustable independently gain.This is favourable, because small opening can be near one of first and second sensors, thereby can require bigger gain away from the sensor of this small opening.First and second signal conditioning units 10 and 11 gain are transmitted to treating apparatus 6.

Preferably, the gain of the gain of first signal conditioning unit 10 and secondary signal regulon 11 is set as same amount.This configuration keeps the transport function of sensor, and this configuration produces accurate result when with the systematic comparison of adopting automatic gain to control.

From signal conditioning unit 10 and the 11 first and second filtered signals, be sent out unit 12 and 13 respectively and receive.Transmitting element 12 and 13 comprises antenna 14 and 15 respectively, is used for wirelessly sending data.Transmitting element 12 is arranged to send signal from the detection of first sensor 4 to receiver 16.Transmitting element 13 is arranged to send signal from the detection of second sensor 5 to receiver 16.Transmitting element 12 and 13 operates in UHF (the License Free UHF) scope that need not licence, 10Hz is arranged to the frequency response of 18Hz, greater than the signal to noise ratio (S/N ratio) of 110dB with reduce the HDX compander of noise.

Receiver 16 sends first signal and the secondary signal that receive to treating apparatus 6.Treating apparatus 6 at first uses analog to digital converter 17, from the signal of first sensor 4 and from second sensor 5 signal digitalized.Analog to digital converter has the resolution of 12 bit per sample, and sampling rate is set as 2.5kHz.Then, digital signal is recorded unit 18 records.This record cell 18 generally includes the hard disk drive of computing machine.Treating apparatus 6 comprises meticulous filter unit 19, and this meticulous filter unit comprises the digital filter that is arranged first and second signal filterings that be recorded, numeral.

Meticulous filter unit 19 is fit to filtering to 1Hz at interval.Meticulous filter unit 19 comprise Bezier finite impulse response (FIR) (FIR) wave filter and, especially the 9th rank Bezier low-pass filter and the 8th rank Bezier Hi-pass filter.Ending of low-pass filter is set to 350Hz basically, and ending of Hi-pass filter is set to 15Hz basically.Have been found that these settings are especially favourable to the MDPE pipe.If the user does not know tube material, they can set this meticulous filter unit 19 for example makes 10Hz pass through to the wide bandwidth of 760Hz, and observed frequency spectrum results then is to determine appropriate frequency scope of checking to be checked.More go through below this point.Bezier FIR wave filter has the group delay of maximum Horizon.They also have linear phase response, and the waveform of their holding signals in passband, and this point makes the destruction minimum to the linear phase-frequency relation of small opening signal.Have been found that this selection of digital filter, especially favourable to isolating the small opening signal.The maintenance of linear phase-frequency relation is important, because this relation can make the calculating of speed of small opening signal accurate especially, as discussing in more detail below.Also have, the high-order Bessel filter has high roll-off rate and better linear flat passband, and it helps to keep this relation.

Then, first and second signals from meticulous filter unit 19 are sent to windowing unit 20.Windowing unit 20 the Hanning window mouth so that overlapping these signals that is applied to of 50% to be arranged between the window.Obtain like this from first signal of a plurality of windowings of first sensor 4 with from the secondary signal of a plurality of windowings of second sensor 5.The width of Hanning window mouth is set to the size of the Fast Fourier Transform (FFT) of being undertaken by converter unit 21 that makes that it equals to discuss below.Get 50% overlapping circular effect of window with the Fast Fourier Transform (FFT) avoiding being undertaken by converter unit 21.Also have, because window is in the shape at its edge, this is overlapping guarantees also to be considered at the small opening signal of window edge.Windowing unit 20 is arranged to make the small opening signal windowing from first digitized samples.

Converter unit 21 is arranged the secondary signal of first signal of each windowing and each windowing is carried out Fast Fourier Transform (FFT).Now, these signals can be further processed at frequency domain.It is that 1024 Fast Fourier Transform (FFT) (FFT) is carried out that conversion is to use size.If any in sampling rate, frequency resolution and the time delay length must be changed, its size can be changed.1024 default value is chosen, because the typical range D that the small opening detecting device is operated thereon is approximately 100m.The average velocity of small opening signal approximately is 350m/s, thereby about 0.3 second sampling needs, and is detected by two sensors 4,5 to guarantee the small opening signal.Therefore, when being sampled with 2.5Hz, about 1024 need.See that easily different counting can be used, and depends on the setting of system.

The next processing unit for the treatment of apparatus 6 comprises asks averaging unit 22.Ask averaging unit 22 to be fit to calculate root mean square between the windowing signal of 10 to 25 FFT conversion.In the present embodiment, on average being determined on 15 windowing signals.Noise in the small opening signal is at random on amplitude and phase place.When asking when on average being performed, overall noise level descends, because have been found that the signal from the small opening signal is very constant.

Then, this average signal can show to the user with the mode of display device.Signal is shown to the user the amplitude of frequency and time, so that can make the frequency range of the small opening signal that occurs in their recognition result.As discussed above, if necessary, the user can regulate the setting of meticulous filter unit 19, on the frequency range that is aligned to (focus on) concern.As an alternative, treating apparatus 6 can comprise the small opening signal frequency determining unit (not showing) that is used to select frequency range.This small opening signal frequency determining unit can be implemented with the algorithm of handling from the output of asking averaging unit 22.

Cross-correlation unit 23 receives carries out simple crosscorrelation from the result of windowing unit 20 and to each the windowing signal of tackling mutually from the first sensor 4 and second sensor 5, to obtain related function.Therefore, from the first windowing signal of first sensor 4, be fit to and the first windowing signal simple crosscorrelation from second sensor 5.Then, cross-correlation unit 23 be fit to make from the second windowing signal of first sensor 4 and (from) second sensor 5 (the second windowing signal) simple crosscorrelation, the rest may be inferred by analogy.Cross-correlation unit 23 is adapted at operating in the frequency domain and carrying out using pre-filtering before the simple crosscorrelation.In the present embodiment, unit 23 is to signal application smoothing coherence transfer (SCOT) weight factor.See that easily this signal comprises much noise.Have been found that the application of SCOT weight factor before simple crosscorrelation, it is particularly advantageous that the signal that much noise is arranged is obtained accurate simple crosscorrelation.The SCOT weighting function comes to a point the peak value in the cross correlation function that obtains, and also makes frequency zones decay affected by noise.

Cross-correlation unit 23 determines whether this cross correlation function contains indication and wait to reconnoitre the distinguishing peak value that small opening exists in the pipe 3.The user can discern distinguishing peak value in result's diagrammatic representation.Then, the position of this distinguishing peak value can be input into small opening positioning unit 24 by the user.As an alternative, can use peak detection algorithm, such as " peak value is determined (the peakdet) " algorithm among the Matlab, this algorithm is implemented by those of skill in the art easily.

If cross-correlation unit 23 determines to exist small opening, then small opening positioning unit 24 is used to calculate the small opening position.Determine this position, small opening positioning unit 24 needs the speed of small opening signal, and locates time delay between received small opening signal and another small opening signal at one of first and second sensors 4,5.This time delay can extract from the related function that is calculated by cross-correlation unit 23.This speed is calculated by speed determining unit 25.

Therefore, treating apparatus 6 also comprises speed determining unit 25.Linear phase-frequency relation feature that speed determining unit 25 is fit to from the small opening signal derives the speed of small opening signal.Especially, have been found that individual other of small opening signal changes with frequency linearity ground with relative phase place both, and speed can be from the gradient calculation of this linear phase frequency relation.

The small opening signal characteristic depends on wave number, and for the elastic housing that is full of by liquid, such as polyethylene pipe, this wave number changes quite greatly.In practice, any small opening in the pipe has many ripples in the pipe; Yet, have been found that and have only a kind of ripple that (s=0 n=0) plays a leading role, and carries most of energy by pipe and liquid in the small opening propagation of noise.To this ripple, it is uniformly that acoustic stress can be considered to cross over the transversal section, and at frequency domain, this pressure is provided by following formula:

P(L)＝P ₀(ω)e ^-jkL＝P ₀(ω)e ^-ωαLe ^-jωL/c (4)

Here L is the distance between small opening position and the sensing station, P ₀Be the amplitude of acoustic stress at the L=0 place; K is (fluid-borne) wave number that is had by the plural liquid that k=ω/c-j α ω provides, and phase place (φ) is provided by following formula:

φ＝-ωL/c (5)

Can see that the small opening signal is the index attenuation function and negative phase place is arranged.With reference to top equation, for characteristic frequency, phase dependent in sensing station from the distance of small opening location and the speed of small opening signal.The result is that to constant distance and speed, phase place will change with frequency linearity ground.Therefore, we have found that the speed of small opening signal can be calculated from the slope of the linear relationship between phase place and the frequency.

Fig. 3 diagrammatically illustrates the speed of small opening signal and how to calculate.Calculate the speed of small opening signal, multiplied each other (multiplied) and infinitely-great in theory observation interval (T) is gone up by average, so that make from the Fourier transform of first signal of converter unit 21 and secondary signal:

$S_{x_1{x}_2}^m\left(\mathrm{\&omega;}\right)=\underset{T\&RightArrow;\&infin;}{\mathrm{Lim}}\frac{1}{T}{\&Integral;}_{-\&infin;}^{\&infin;}{\&Integral;}_{-\&infin;}^{\&infin;}{\left(P_0\left(\mathrm{\&omega;}\right)\right)}^2{e}^{-\mathrm{\&alpha;\&omega;}({\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="HDA0000078786960000012.png"\; state="\{\{state\}\}">L</figure-callout>}}_1+L_2)}{e}^{-\mathrm{j\&omega;}({\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="HDA0000078786960000012.png"\; state="\{\{state\}\}">L</figure-callout>}}_1+L_2)/c}\mathrm{dfd\&tau;}$

$=S_{\mathrm{ll}}\left(\mathrm{\&omega;}\right){\mathrm{\&Psi;}}^m\left(\mathrm{\&omega;}\right)e^{-\mathrm{j\&omega;}({\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="HDA0000078786960000012.png"\; state="\{\{state\}\}">L</figure-callout>}}_1+L_2)/c}---\left(6\right)$

Here L ₁And L ₂Be the first sensor 4 and second sensor 5 from the position separately of small opening 2, as shown in fig. 1, S _Ll(ω) be the small opening signal automatic spectral density (auto-spectral density) and

${\mathrm{\&Psi;}}^m\left(\mathrm{\&omega;}\right)=\left|p_1(\mathrm{\&omega;},L_1)p_2(\mathrm{\&omega;},L_2)\right|={\left|p_0\left(\mathrm{\&omega;}\right)\right|}^2{e}^{-\mathrm{\&omega;\&alpha;}({\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="HDA0000078786960000012.png"\; state="\{\{state\}\}">L</figure-callout>}}_1+L_2)}={\left|p_0\left(\mathrm{\&omega;}\right)\right|}^2{e}^{-\mathrm{\&omega;\&alpha;D}}---\left(7\right)$

Here D is the total distance between first and second sensors, and p ₁(ω, L ₁) and p ₂(ω, L ₂) be illustrated respectively in the Fourier transform of the small opening signal of measuring on the first sensor and second sensor.The phase place of product that the independent variable of equation 7 provides two small opening signal Fourier transforms is as follows:

${\mathrm{\&phi;}}_{x_1{x}_2}^m\left(\mathrm{\&omega;}\right)=\mathrm{Arg}\left\{S_{x_1{x}_2}^m\left(\mathrm{\&omega;}\right)\right\}=-\mathrm{\&omega;}({\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="HDA0000078786960000012.png"\; state="\{\{state\}\}">L</figure-callout>}}_1+L_2)/c=-\mathrm{\&omega;D}/c---\left(8\right)$

Here

Be the first signal (x ₁) Fourier transform and secondary signal (x ₂) the phase place of product of Fourier transform.Can release from equation (8), the phase place of the product of the small opening signal Fourier transform of measuring on two location changes linearly with frequencies omega.As long as distance D is known, speed c can from

And the slope of this linear relationship calculates between the angular frequency, and D can in all sorts of ways, and very accurately measures such as measuring wheel/band.The benefit of this method is, speed can determine from measured signal, there is no need to adopt the method that is used for estimated speed of prior art or is used for measuring speed and simulates small opening.This method needs the total distance (D) between two sensing stations, can be considered so pipe is gone up any small opening.Have been found that this method produces accurate result.By guaranteeing the high coherence between the signal of measuring on the first sensor and second sensor, degree of accuracy can further be modified.This degree of accuracy can further be modified by using short transducer spacing D.

So small opening positioning unit 24 is fit to calculate small openings from the distance of first sensor 4 and the small opening distance from second sensor 5.If it is t that the small opening signal propagates into first sensor position required time from small opening position 2 ₁, and be t to second sensing station ₂, (first sensor is x to measured signal so ₁(t) and second sensor is x ₂(t)) time delay between is relevant with the small opening location:

${\mathrm{\&tau;}}_{\mathrm{shift}}=t_2-{\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="HDA0000078786960000011.png"\; state="\{\{state\}\}">t</figure-callout>}}_2=\frac{L_2-L_1}{c}---\left(9\right)$

Here c is the velocity of propagation of small opening signal in pipe 3 and the water column, and L ₁And L ₂It is respective sensor position 1 and 2 from the small opening position.If the total distance (L between two sensing stations ₁+ L ₂) be D, then small opening is provided by following formula with respect to the position of sensing station 1

${\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="HDA0000078786960000012.png"\; state="\{\{state\}\}">L</figure-callout>}}_1=\frac{D-c{\mathrm{\&tau;}}_{\mathrm{shift}}}{2}---\left(10\right)$

Coherence unit 26 can be used to determine to carry out the frequency of simple crosscorrelation thereon.Therefore, under the situation of the distinguishing peak value of cross-correlation unit 23 nonrecognition, it can send first and second signals to coherence unit 26 for further handling.Coherence unit 26 from meticulous filter unit 19 receive the signal related with first sensor 4 and with the related signal of second sensor 5.Coherence unit 26 is arranged to definite coherence from first sensor 4 signal that starts and the signal that starts from second sensor 5.The coherence of two signals represents the correlation degree of two signals by 0 to 1 scale.The coherence is relevant more near 1, two signal more.The coherence of two signals is calculated on each frequency.When the coherence when the small opening signal that obtains from first and second sensing stations is performed, it will produce the coherence value of each frequency, for example the MDPE to this setting manages, and is from 15Hz to 350Hz.The frequency that the coherence is the highest is considered to be performed relevant frequency range.The frequency range of being determined by coherence unit 26 is arranged so that be sent to cross-correlation unit 23, so that can be performed simple crosscorrelation on the frequency range that is identified.

Process flow diagram shown in Fig. 2 shows the embodiment of the method for operating of small opening detecting device.

On behalf of first sensor 4, step 30 detect the signal of the hose saddle 7 that adheres to from it.Similarly, step 31 shows that second sensor 5 is simultaneously from second hose saddle, 8 picked up signal.Step 30 and 31 is to carry out on predetermined measurement period T.In the present embodiment, T was set to 5 minutes.

Step 32 representative is from the signal of first sensor 4, and this signal is that the low-pass filter by signal conditioning unit 10 is transmitted, and this low-pass filter is set and transmits the following frequency of 760Hz.Step 33 representative is from the signal of second sensor 5, and this signal is that the low-pass filter by signal conditioning unit 11 is transmitted, and this low-pass filter is set and transmits the following frequency of 760Hz.

Step 34 and step 35 comprise the filtered signal from step 32 and 33, and these signals were exaggerated device 12 and 13 respectively and amplify before the transmission of step 36 and 37.

These signals are received device 16 in step 38 and receive, then in step 39 by the analog to digital converter digitizing, these signals are recorded in step 40 again thereafter.Should be pointed out that two arrows represent the path of signal between each step, because the small opening signal of deriving from first sensor 4 with the small opening signal of deriving from second sensor 5, is processed dividually.

The application of the meticulous filter unit 19 of step 41 representative.In step 41, the 9th rank Bezier low-pass filter and the 8th rank Bezier Hi-pass filter are applied to digitized signal.If tube material is known, suitable frequency range can be selected by default value.For example, the small opening signal in the MDPE pipe appears at 15 usually to the 350Hz scope.If tube material is not known, this step will relate to 10 to 760Hz meticulous filtering.

From the meticulous filtering signal of step 41, thereafter in step 42 by windowing unit 20 windowings.The Hanning window mouth is with overlapping this meticulous filtering signal that is applied to of 50% between the window.Obtain a plurality of windowing signal and a plurality of windowing signals that start from second sensor 5 that start from first sensor 4 like this.

In step 43, Fast Fourier Transform (FFT) is transformed unit 21 and is applied to the windowing signal.These a plurality of signals can be further processed in frequency domain now.

In step 44, about 15 Fourier transforms from the windowing signal of first sensor, it is average to be asked averaging unit 22 to calculate root mean square (RMS).Similarly, about 15 Fourier transforms from the windowing signal of second sensor, it is average to be calculated RMS.

In step 45, ask the result of averaging unit 22 to show to the user.The user can discern the frequency of small opening signal appearance and these frequencies are imported, with the meticulous filtering of harmonizing (to focus) meticulous filter unit 19.As an alternative, this process can be by robotization, and conclusion is fed back to meticulous filter unit 19.Therefore, this method can be returned step 41 for further meticulous filtering.Otherwise this method advances to step 46.See that easily if tube material is known, step 43,44 and 45 can not carried out, and this method can directly advance to step 46.

Step 46 comprises the windowing signal from first sensor 4, with the process from the simple crosscorrelation of the corresponding windowing signal of second sensor 5.

The coherence between two signals is determined in step 47 representative, so that simple crosscorrelation can be carried out on the relevant frequency range of topnotch.See that easily the step 47 that the coherence determines is chosen wantonly, and replacement is that simple crosscorrelation can be carried out on the frequency range of being determined by meticulous filter unit 19.

If small opening is detected by existing of distinguishing peak value in the related function, this method advances to step 48, and step 48 comprises from the linear phase-frequency relation of signal determines speed.

In case speed is determined, step 49 shows, use speed, the time delay between their reception on one of sensor 4,5 and another sensor and the distance between the first sensor position and second sensing station of signal, small opening is located.

See easily, though present embodiment be described with regard to finding out small opening in the relevant intermediate density polyethylene pipe,, such as in the above discussion, by changing the setting of digital filter, present embodiment can be used to locate the small opening in the pipe of other materials effectively.

Claims (21)

1. small opening detecting device that is used for detecting and locating the plastic water supply pipe small opening, this small opening detecting device comprises: first sensor is arranged at and detects the small opening signal of propagating along pipe on the primary importance; Second sensor, be arranged at the isolated second place of primary importance on detect along the small opening signal of this pipe propagation; With the treating apparatus that is fit to from the first sensor and the second sensor received signal, this treating apparatus is fit to the measurement from the small opening signal characteristic, determine the speed of this signal, and use distance between this speed and the first sensor and second sensor, determine the location of small opening.

2. according to the small opening detecting device of claim 1, wherein this feature is the phase place and the frequency of small opening signal.

3. according to the small opening detecting device of claim 1 or claim 2, wherein this treating apparatus is fit to use linear relationship between the phase place of this small opening signal and the frequency, determines the speed of small opening signal.

4. according to each small opening detecting device of front claim, wherein this first and second sensor respectively comprises signal conditioning unit and transmitting element, this signal conditioning unit is arranged the signal filtering to the respective sensor reception, and this transmitting element is fit to send this filtered signal to treating apparatus.

5. according to the small opening detecting device of claim 4, wherein signal conditioning unit comprises wherein the passband low-pass filter below 760Hz basically.

6. according to the small opening detecting device of claim 4 or claim 5, wherein this small opening detecting device comprises transmitting element and receiving element, be arranged to make first sensor and second sensor together with they related signal conditioning units, can wirelessly operate the remainder of small opening detecting device, and wherein this transmitting element is fit to the phase place and the phase place that keep by the small opening signal of second sensor of maintenance by the small opening signal of first sensor detection.

7. according to each small opening detecting device of front claim, wherein this treating apparatus is fit to the signal digitalized and storage that receives from first sensor and second sensor.

8. according to each small opening detecting device of front claim, wherein this treating apparatus comprises meticulous filter unit, is fit to the small opening signal filtering to being digitized, and this meticulous filter unit comprises Bezier finite impulse response (FIR) (FIR) wave filter.

9. according to the small opening detecting device of claim 8, wherein this meticulous filter unit comprises the 9th rank Bezier low-pass filter and the 8th rank Bezier Hi-pass filter.

10. according to each small opening detecting device of front claim, wherein this treating apparatus comprises the windowing unit, be fit to the Hanning window mouth is applied to from the signal of first sensor acquisition, to obtain the signal of a plurality of windowings, and be applied to from the signal of second sensor acquisition, to obtain the signal of a plurality of windowings.

11. according to the small opening detecting device of claim 10, wherein this treating apparatus comprises converter unit, is fit to split window signal and uses Fast Fourier Transform (FFT).

12. small opening detecting device according to claim 10 or claim 11, wherein this treating apparatus comprises and asks averaging unit, this asks averaging unit to be suitable for: after each windowing signal application Fourier transform, calculating is average from the root mean square of a plurality of windowing signals of first sensor; And after each windowing signal application Fourier transform, calculating is average from the root mean square of a plurality of windowing signals of second sensor.

13. according to each small opening detecting device of front claim, wherein this treating apparatus comprises the speed determining unit, be arranged to determine the speed of small opening signal from distance between the feature of small opening signal and the first sensor and second sensor, wherein this speed is obtained by following equation:

$c=\frac{-\mathrm{\&omega;D}}{{\mathrm{\&phi;}}_{x_1{x}_2}^m\left(\mathrm{\&omega;}\right)}$

Here c is made of the speed of signal, and ω represents angular frequency, and D is a distance between first and second sensor, and

Be the first signal (x from first sensor ₁) Fourier transform with from the signal (x of second sensor ₂) the phase place of product of Fourier transform.

14. small opening detecting device according to claim 13, wherein this treating apparatus comprises the small opening positioning unit, be fit to receive the speed of calculating by the speed determining unit, this small opening positioning unit also is fit to carrying out simple crosscorrelation from the signal of first sensor and signal from second sensor, and use this cross correlation results and this speed, calculate the location of this small opening with respect to the first sensor position or second sensing station.

15. a method that detects small opening position in the plastic tube comprises step:

Along monitoring the small opening signal on the primary importance of pipe;

Along pipe with the isolated second place of primary importance on monitor the small opening signal;

Determine the sensor spacing distance between the primary importance and the second place;

Determine the speed of small opening signal from signal characteristic; With

Use this sensor spacing distance and speed, the location of identification small opening.

16. according to the method for claim 15, the location of wherein discerning small opening also comprises the time delay of using between the small opening signal that related function determines to receive on the first sensor and second sensing station; With

Use this sensor spacing distance, this speed and this time delay, the location of identification small opening.

17. according to the method for claim 15, wherein should monitor the step of the signal of indication small opening, on predetermined measurement period, carry out.

18. according to the method for claim 15 or claim 16 or claim 17, wherein this method comprises the step of the signal that receives on the signal that obtains on the primary importance and the second place being carried out simple crosscorrelation.

19. according to each method in the claim 15 to 18, wherein this method comprises by having determined whether distinguishing peak value obtainedly, confirms small opening detected step in related function.

20. according to the method for claim 18, simple crosscorrelation wherein is to carry out on the frequency range of small opening signal between 0Hz and the 350Hz.

21. one kind basically by describe with reference to Fig. 1 of accompanying drawing at this and at the small opening detecting device of the illustrated type shown in this Fig. 1.

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